A welding robot generally comprises a stand pivotally receiving a trunk-forming portion having connected thereto via a hinge known as a “shoulder” an articulated arm having a free end that is provided with a clamp fitted with welding electrodes.
The pressure exerted on the metal sheets by the welding electrodes, and the heat generated by electrical currents passing through the electrodes leads to the electrodes becoming deformed, tending to increase the contact area between the electrodes and the metal sheets. This reduces the density of the current flowing through the electrodes, so it is necessary periodically to increase the current level, and then once the deformation becomes too great, it is necessary to grind the electrodes in order to return them to their initial shape.
Such grinding is performed using a grinder secured to the ground or to the platform supporting the robot, and in the vicinity of the robot.
The positioning of the grinder must be taken into account when programming the movements of the robot, firstly in order to bring the clamp into the grinder, and secondly in order to ensure that the movements of the robot do not interfere with the grinder during welding operations.
The positioning of the grinder is also taken into account while programming adjacent robots so that their movements do not lead to them bumping into the grinder.
The paths followed by cableways receiving cables for powering robots and grinders also depend on the positioning of the grinder.
Unfortunately, once a robot has been installed in the line in which it is to work, it can happen that the grinder cannot be positioned in the initially intended position. For example, this can be the result of a manhole cover or an expansion joint preventing the grinder being secured to the ground.
It is then necessary to reposition the grinder and thus to correct the programming of the robot, and possibly also of adjacent robots, and to reorganize the paths of the cableways.
The same applies when the robot and the grinder are mounted on a platform: the presence of beams, cables, or openings can interfere with installing the grinder.
A robot is described, in particular in U.S. Pat. No. 6,339,204, that has a grinder secured to the stand of the robot. With the grinder mounted on the robot, the power supply cabling to the grinder can be combined with the power supply cabling to the robot. In addition, the grinder is secured to the ground as a result of the robot being secured to the ground, so no additional operations are required. Nevertheless, the grinder can still interfere with the movements of the robot or with the movements of its neighbors, and its position needs to be taken into account when programming the robot.